In the settlement of the estate of Mr. Barbera who died intestate, his wife renounced her inheritance and her share of the conjugal property in favor of their children. The BIR determined that there was a taxable gift and thus assessed Mrs. Barbera as a donor.

Kasi po kapag isa or iilan lang sa co heirs you are exercising acts of ownership, hence instead of pure renunciation you are actually accepting the inheritance and when you renounce in favor of the particular heir/s ( but not all) they are actually inheriting or accepting from you unlike if renunciation is in favor of ALL co heirs , they are still inheriting from the decedent since by law it would properly accrue to them also.